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ease, marked by the appearance of trypanosomes in the blood, negroes show no 

 symptoms as a rule, though whites are subject to fever. The symptoms may ap- 

 pear as early as four weeks after infection or as late as seven years. 



"In the second stage trypanosomes appear in the cerebro-spinal fluid and in 

 large numbers in the glands, those of the neck, axillae and groins becoming en- 

 larged. There is tremor of the tongue and hands, drowsiness, emaciation and 

 mental degeneration. The drowsiness passes into periods of lethargy which be- 

 come gradually stronger until the patient becomes comatose and dies. Some vic- 

 tims do not sleep excessively but are lethargic and profoundly indifferent to all 

 going on around them." 



Late investigations go to show "that Glossina morsitans may act as a host 

 for a human trypanosome which is probably identical with T. gamhiense" . Prob- 

 ably also "that some of the vertebrates other than man may harbour T. gambiense 

 and that there is a possibility of these things being transmitted to man" (Doane). 



With regard to the development of T. gambiense in Glossina palpalis it is 

 known that "two days after biting an infected animal the fly becomes incapable 

 of infecting other animals and remains so for about 22 to 28 days, when it again 

 becomes infective and may remain so for at least 96 days. During the infection 

 period the salivary glands are found to be invaded with the type of the trypano- 

 some that is found in the vertebrate blood" (Doane). 



Rat Fleas and Plague. 



Plague, known in three forms as bubonic, septicaemic and pneumonic, is 

 caused by Bacillus pestis which attacks rats, mice, cats, dogs and other domestic 

 animals. The disease is transmitted mainly by fleas, sometimes by bed-bugs, and 



The cat and dog flea : (a) egg ; {d) larva of maggot 

 (c( adult, much enlarged. 



the wounds made by the bites allow entrance to plague bacilli. "Plague is primar- 

 ily a disease of rats, an epidemic of plague in these animals having often been 

 observed to precede as well as to accompany an epidemic among human beings." 



